Magnetic recording medium, method for manufacturing same, and film-forming apparatus

ABSTRACT

A magnetic recording medium including a base material which has flexibility, and a laminated film, in which a variation in magnetic characteristics is within ±10% over a division of 300 m in a longitudinal direction of the base material.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority to Japanese Priority PatentApplication JP 2014-074954 filed in the Japan Patent Office on Mar. 31,2014, the entire content of which is hereby incorporated by reference.

BACKGROUND

The present technology relates to a magnetic recording medium where alaminated film is provided on a base material which has flexibility, amethod for manufacturing the same, and a film-forming apparatus forproducing the laminated film.

In recent years, due to the development of information technology (IT)in society, movements toward electronic formats in libraries, NationalArchives, and the like, and the prolonged storage of business documents,there has been an increased demand for increasing the recording densityof magnetic tape for data storage.

As a method for manufacturing a magnetic tape with a high recordingdensity, a method has been proposed which, while moving a flexible basematerial which has a strip shape, film-forms a laminated film on thebase material by a sputtering method, a vapor deposition method, or thelike. Japanese Unexamined Patent Application Publication No. 2006-286115(refer to paragraphs [0013] and [0055]), Japanese Unexamined PatentApplication Publication No. 2005-353191 (refer to paragraph [0031]), andJapanese Unexamined Patent Application Publication No. 07-110939 (referto paragraph [0016]) describe that, in this type of manufacturingmethod, before film-forming the laminated film on the flexible basematerial, a process of degassing the base material is carried out (forexample, refer to Japanese Unexamined Patent Application Publication No.2006-286115 (refer to paragraphs [0013] and [0055]), Japanese UnexaminedPatent Application Publication No. 2005-353191 (refer to paragraph[0031]), and Japanese Unexamined Patent Application Publication No.07-110939 (refer to paragraph [0016])).

SUMMARY

It is desirable to provide a magnetic recording medium which hasexcellent reliability, a method for manufacturing the same, and afilm-forming apparatus for producing the laminated film.

According to an embodiment of the present technology, there is provideda magnetic recording medium including a base material which hasflexibility, and a laminated film, in which a variation in magneticcharacteristics is within ±10% over a division of 300 m in alongitudinal direction of the base material.

According to another embodiment of the present technology, there isprovided a film-forming apparatus including a rotating body which movesa base material with a strip shape which has flexibility, a plurality ofcathodes which are provided to oppose a rotating surface of the rotatingbody, and a plurality of accommodating sections which accommodate eachof the plurality of cathodes.

According to still another embodiment of the present technology, thereis provided a method for manufacturing a magnetic recording mediumincluding sequentially film-forming a plurality of thin films on thebase material using a plurality of cathodes which are provided on amoving path of the base material while moving the base material with astrip shape which has flexibility, in which each of the plurality ofcathodes is accommodated in a plurality of accommodating sections.

As described above, it is possible to realize a magnetic recordingmedium which has excellent reliability according to the presenttechnique.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional diagram which schematically shows oneexample of a configuration of a magnetic recording medium according toone embodiment of the present technique;

FIG. 2 is a schematic diagram which shows one example of a configurationof a sputtering apparatus which is used for manufacturing a magneticrecording medium according to one embodiment of the present technique;

FIG. 3A is a schematic diagram which shows a state of a cathodeaccommodating chamber before a heating process, FIG. 3B is a schematicdiagram which shows a state of a cathode accommodating chamber during aheating process, and FIG. 3C is a schematic diagram which shows a stateof a cathode accommodating chamber during a cooling process;

FIG. 4 is a cross-sectional diagram which schematically shows oneexample of a configuration of a magnetic recording medium according to amodified example 1 of one embodiment of the present technique;

FIG. 5 is a cross-sectional diagram which schematically shows oneexample of a configuration of a magnetic recording medium according to amodified example 2 of one embodiment of the present technique;

FIG. 6A is a diagram which shows a relationship between an inner wallsurface temperature of a cathode accommodating chamber and an H₂Opartial pressure inside the cathode accommodating chamber, and FIG. 6Bis a diagram which shows a relationship between an H₂O partial pressureinside a cathode accommodating chamber and coercive force of a magnetictape;

FIG. 7A is a diagram which shows a relationship between a sputteringdischarge time and an inner wall surface temperature of a cathodeaccommodating chamber, and FIG. 7B is a diagram which shows arelationship between a sputtering discharge time and coercive force of amagnetic tape;

FIG. 8A is a diagram which shows a relationship between a sputteringfilm-forming length and an H₂O partial pressure inside a cathodeaccommodating chamber, and FIG. 8B is a diagram which shows arelationship between a sputtering film-forming length and coercive forceof a magnetic tape; and

FIG. 9A is a diagram which shows a relationship between a sputteringfilm-forming length and a squareness ratio of a magnetic tape, and FIG.9B is a diagram which shows a relationship between a sputteringfilm-forming length and orientation strength Δθ₅₀ of a magneticrecording layer of a magnetic tape.

DETAILED DESCRIPTION

In the present technique, a laminated film preferably includes a lowercoating layer and a perpendicular recording layer and more preferablyincludes at least one layer out of an intermediate layer, a softmagnetic layer, and a CAP layer.

In the present technique, each layer of the lower coating layer, theintermediate layer and the perpendicular recording layer may be any of asingle layer structure and a multi-layer structure. It is preferable toadopt a multi-layer structure from the viewpoint of further improvingmagnetic characteristics and/or recording and play back characteristicsof a magnetic recording medium. It is preferable to adopt a multi-layerstructure with a two-layer structure when considering manufacturingefficiency.

In the present technique, the magnetic recording medium is preferablyfurther provided with a soft magnetic layer between the base materialand the lower coating layer or between the lower coating layer and theintermediate layer. Either of a single layer structure or a multi-layerstructure may be used as the structure of the soft magnetic layer;however, it is preferable to use a multi-layer structure from theviewpoint of improving recording and play back characteristics. It ispreferable that the soft magnetic layer which has the multi-layerstructure is provided with a first soft magnetic layer, an intermediatelayer, and a second soft magnetic layer, in which the intermediate layeris provided between the first soft magnetic layer and the second softmagnetic layer. In a case where the magnetic recording medium is furtherprovided with the soft magnetic layer, it is preferable for a lowercoating layer to be provided between the soft magnetic layer and thelower coating layer.

In the present technique, it is preferable for the lower coating layer,which has an amorphous state and includes an alloy which includes Ti andCr, to be provided on the base material surface. Due to this, it ispossible to suppress an influence which O₂ gas, H₂O, or the like whichis adsorbed on a base material surface has with respect to anintermediate layer and/or a recording layer and to improve smoothness onthe base material surface.

Description will be given of embodiments of the present technology inthe following order.

1. Configuration of Magnetic Recording Medium

2. Configuration of Sputtering Apparatus

3. Method for Manufacturing Magnetic Recording Medium

4. Effects

5. Modified Examples

1. Configuration of Magnetic Recording Medium

As shown in FIG. 1, a magnetic recording medium according to oneembodiment of the present technology is a so-called single layerperpendicular magnetic recording medium and is provided with a basematerial 11 and a laminated film 10. The laminated film 10 is providedwith a lower coating layer 12 which is provided on a surface of the basematerial 11, an intermediate layer 13 which is provided on a surface ofthe lower coating layer 12, and a magnetic recording layer 14 which isprovided on a surface of the intermediate layer 13. The laminated film10 may be further provided with a protective layer 15 which is providedon a surface of the magnetic recording layer 14 and a top coat layer 16which is provided on a surface of the protective layer 15 according tonecessity.

The lower coating layer 12, the intermediate layer 13, and the magneticrecording layer 14 are film-formed by a physical deposition method. Asthe physical deposition method, a sputtering method is preferable fromthe viewpoints of productivity or the like. Here, in the presentspecification, a recording medium which does not have a soft magneticunderlayer is referred to as a “single layer perpendicular magneticrecording medium” and a recording medium which has a soft magneticunderlayer is referred to as a “two-layer perpendicular magneticrecording medium”.

The magnetic recording medium is suitable for use as a storage media fordata archives for which the demand is expected to increase more and morein the future. The magnetic recording medium is able to realize, forexample, a surface recording density of 10 times or more the currentcoating-type magnetic tape for storage, that is, a surface recordingdensity of 50 Gb/in². In a case of configuring a general linearrecording type data cartridge using a magnetic recording medium whichhas such a surface recording density, it is possible to record with alarge capacity of 50 TB or more for each roll in a data cartridge. Themagnetic recording medium is suitable for use for a recording and playback apparatus which uses a ring type recording head and a giantmagnetoresistive (GMR) type play back head.

The variation in the magnetic characteristics is within ±10%, preferablywithin ±5%, over a division of 300 m in the longitudinal direction ofthe base material 11. By the variation in the magnetic characteristicsbeing within ±10%, the characteristic stability is maintained and it ispossible to obtain a magnetic recording medium which has excellentreliability. Here, the magnetic characteristics are at least onecharacteristic out of a holding power Hc, a squareness ratio Rs, and anorientation strength Δθ₅₀ of the magnetic recording layer 14, preferablyall of these characteristics. Here, the orientation strength Δθ₅₀ isobtained by measuring a diffraction peak of magnetic atoms which areincluded in the magnetic recording layer 14 in X-ray diffraction peaksof the magnetic recording medium using a locking curve method.

Base Material

The base material 11 which is a support body is, for example, a longfilm and has a surface which has a longitudinal direction (an MDdirection) and a short direction (a TD direction). It is preferable touse a nonmagnetic base material which has flexibility as the basematerial 11. It is possible to use, for example, a flexible polymerresin material which is used for a normal magnetic recording medium as amaterial of a nonmagnetic base material. Specific examples of such apolymer material include polyesters, polyolefins, cellulose derivatives,vinyl-based resins, polyimides, polyamides, polycarbonate, or the like.

Lower Coating Layer

The lower coating layer 12 is provided between the base material 11 andthe intermediate layer 13. It is preferable that the lower coating layer12 includes an alloy which includes Ti and Cr and has an amorphousstate. In addition, oxygen (O) may be further included in the alloy. Theoxygen is impure oxygen which is included in a small amount inside thelower coating layer 12 when film-forming the lower coating layer 12 by afilm-forming method such as a sputtering method. Here, “alloy” has themeaning of at least one type of a solid solution, a eutectic body, anintermetallic compound, or the like which includes Ti and Cr. “Amorphousstate” has the meaning that a halo is observed by an electrondiffraction method and that a crystal structure may not be specified.

The lower coating layer 12 which includes an alloy which includes Ti andCr and has an amorphous state has an effect of suppressing the influenceof O₂ gas or H₂O which is adsorbed on the base material 11 and offorming a metallic smooth surface on the surface of the base material 11by easing unevenness of the surface of the base material 11. Due to thiseffect, the perpendicular orientation of the intermediate layer 13 isincreased. Here, when the state of the lower coating layer 12 is acrystal state, the column shape accompanying the crystal growth isclear, the unevenness of the surface of the base material 11 isincreased, and the crystal orientation of the intermediate layer 13deteriorates.

The ratio of oxygen (O) with respect to the total amount of Ti, Cr, andO which are included in the lower coating layer 12 is preferably 15atomic % (at %) or less, more preferably 10 atomic % or less. When theratio of oxygen exceeds 15 atomic %, TiO₂ crystals are generated andthus the orientation of the intermediate layer 13 greatly decreases soas to have an influence on crystal nucleation of the intermediate layer13 which is formed on a surface of the lower coating layer 12.

The ratio of Ti with respect to the total amount of Ti and Cr which areincluded in the lower coating layer 12 is preferably within a range of30 atomic % or more to 100 atomic % or less, more preferably 50 atomic %or more to 100 atomic % or less. When the ratio of Ti is less than 30%,a (100) surface of a body-centered cubic lattice (bcc) structure of Cris orientated and the orientation of the intermediate layer 13 which isformed on a surface of the lower coating layer 12 decreases.

Here, it is possible to determine the ratio of the elements describedabove as follows. Etching is performed using an ion beam from the topcoat layer 16 side of the magnetic recording medium, analysis is carriedout using Auger electron spectroscopy with regard to the top surface ofthe etched lower coating layer 12, and an average atomic number ratiowith respect to the film thickness is the ratio of the elementsdescribed above. In detail, analysis is performed with regard to thethree elements of Ti, Cr, and O and the element content is identifiedaccording to the percentage ratios thereof.

The alloy which is included in the lower coating layer 12 may furtherinclude an element other than Ti and Cr as an additional element.Examples of the additional element include one or more types of elementswhich are selected from a group formed of, for example, Nb, Ni, Mo, Al,W, and the like.

Here, the lower coating layer 12 is not limited to a single layerstructure and may be a multi-layer structure with two or more layers.For example, in a case where the lower coating layer 12 has a two-layerstructure, the lower coating layer 12 is provided with a first lowercoating layer (an upper side lower coating layer) and a second lowercoating layer (a lower side lower coating layer). The first lowercoating layer is provided on the magnetic recording layer 14 side andthe second lower coating layer is provided on the base material 11 side.For the second lower coating layer, it is possible to use the same layeras the lower coating layer 12 described above. The first lower coatinglayer includes, for example, a material with a different composition tothe second lower coating layer. Specific examples of the materialinclude NiW, Ta, or the like. Here, it is possible to regard the firstlower coating layer as not a lower coating layer but an intermediatelayer which is provided between the second lower coating layer and themagnetic recording layer 14.

Intermediate Layer

It is preferable that the intermediate layer 13 has the same crystalstructure as the magnetic recording layer 14. In a case where themagnetic recording layer 14 includes a Co-based alloy, it is preferablethat the intermediate layer 13 includes a material which has the samehexagonal close packing (hcp) structure as a Co-based alloy and that a caxis of the structure is orientated in the vertical direction (that is,the film thickness direction) with respect to the film surface. This isbecause it is possible to improve the orientation of the magneticrecording layer 14 and to make matching of lattice constants of theintermediate layer 13 and the magnetic recording layer 14 comparativelyfavorable. It is preferable to use a material which includes Ru as thematerial which has a hexagonal close packing (hcp) structure and, indetail, a Ru single body or a Ru alloy is preferable. Examples of the Rualloy include a Ru alloy oxide such as Ru—SiO₂, Ru—TiO₂, or Ru—ZrO₂. Inaddition, a material which includes Ni, Ta, or the like may be used inthe intermediate layer 13 instead of the material which includes Ru. Itis possible to use an Ni alloy, for example, such as NiW as a materialwhich includes Ni.

Here, the intermediate layer 13 is not limited to a single layerstructure and may be a multi-layer structure with two or more layers.For example, in a case where the intermediate layer 13 has a two-layerstructure, the intermediate layer 13 is provided with a firstintermediate layer (an upper side intermediate layer) and a secondintermediate layer (a lower side intermediate layer). The firstintermediate layer is provided on the magnetic recording layer 14 sideand the second intermediate layer is provided on the lower coating layer12 side.

As the material of the first intermediate layer and the secondintermediate layer, it is possible to use, for example, the samematerial as for the intermediate layer 13 described above. However, thedesired effects in each of the first intermediate layer and the secondintermediate layer are different and therefore the film-formingconditions for each are different. That is, for the first intermediatelayer, a film structure which promotes a granular structure in themagnetic recording layer 14 which is the upper layer thereof ispreferable and, for the second intermediate layer, a film structure withhigh crystal orientation is preferable.

Magnetic Recording Layer

It is preferable that the magnetic recording layer 14 is a perpendicularrecording layer, in more detail, a granular magnetic layer whichincludes a Co-based alloy from the viewpoint of improving the recordingdensity. The granular magnetic layer is configured by strongly magneticcrystal particles which includes a Co-based alloy and a nonmagneticparticle boundary (a nonmagnetic body) which surrounds the stronglymagnetic crystal particles. In more detail, the granular magnetic layeris configured by columns (columnar crystal) which include a Co-basedalloy and a nonmagnetic particle boundary (for example, an oxide such asSiO₂) which surrounds the columns and magnetically separates eachcolumn. In this structure, it is possible to configure the magneticrecording layer 14 which has a structure where each column ismagnetically separated.

A Co-based alloy has a hexagonal close packing (hcp) structure and the caxis thereof is orientated in the vertical direction (the film thicknessdirection) with respect to the film surface. It is preferable to use aCoCrPt-based alloy which contains at least Co, Cr, and Pt as theCo-based alloy. The CoCrPt-based alloy is not particularly limited andthe CoCrPt-based alloy may further include an additional element.Examples of the additional elements include one or more types ofelements which are selected from a group formed of, for example, Ni, Ta,and the like.

The nonmagnetic particle boundary which surrounds the strongly magneticcrystal particles includes a nonmagnetic metallic material. Here, themetals include semi-metals. It is possible to use at least one of ametal oxide and a metal nitride as the nonmagnetic metallic material andit is preferable to use a metal oxide from the viewpoint of stablymaintaining a granular structure. Examples of metal oxides include ametal oxide which includes at least one or more types of elements whichare selected from a group formed of Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y,Hf, and the like and a metal oxide which includes at least a Si oxide(that is, SiO₂) is preferable. Specific examples thereof include SiO₂,Cr₂O₃, CoO, Al₂O₃, TiO₂, Ta₂O₅, ZrO₂, HfO₂, or the like. Examples ofmetal nitrides include a metal nitride which includes at least one ormore types of elements which are selected from a group formed of Si, Cr,Co, Al, Ti, Ta, Zr, Ce, Y, Hf, and the like. Specific examples thereofinclude SiN, TiN, AlN, or the like.

It is preferable that the magnetic recording layer 14 has the averagecomposition shown in the following formula from the viewpoint ofrealizing further improvement of a signal-noise ratio (SNR). This isbecause it is possible to suppress an influence of a demagnetizing fieldand realize a saturation magnetization quantity Ms which is able tosecure a sufficient play back output, and it is possible to secure ahigh SNR due to this.

(Co_(x)Pt_(y)Cr_(100-x-y))_(100-z)—(SiO₂)_(z)

(here, in the formula, x, y, and z are respectively values within arange of 69≦x≦72, 12≦y≦16, and 9≦z≦12).

Here, it is possible to obtain the composition described above asfollows. Etching is performed using an ion beam from the top coat layer16 side of a magnetic recording medium, analysis is carried out by Augerelectron spectroscopy with regard to the top surface of the etchedmagnetic recording layer 14, and an average atomic number ratio withrespect to the film thickness is determined as the composition describedabove. In detail, analysis is performed with regard to the five elementsof Co, Pt, Cr, Si, and O and the element content is identified accordingto the percentage ratios thereof.

A magnetic recording medium according to the present embodiment is asingle layer magnetic recording medium which does not have a underlayer(a soft magnetic underlayer) which includes a soft magnetic material;however, in this type of magnetic recording medium, there is a tendencyfor sufficient recording in the vertical direction to be difficult whenthe influence of a demagnetizing field which is caused by the magneticrecording layer 14 is great in the vertical direction. Since thedemagnetizing field becomes large in proportion to the saturationmagnetization quantity Ms of the magnetic recording layer 14, it isdesirable to make the saturation magnetization quantity Ms small inorder to suppress the demagnetizing field. However, when the saturationmagnetization quantity Ms is small, a residual magnetic quantity Mr issmall and the play back output decreases. Accordingly, it is preferableto select a material which is included in the magnetic recording layer14 from the viewpoint of obtaining both of suppression of the influenceof the demagnetizing field (that is, reduction of the saturationmagnetization quantity Ms), and the residual magnetic quantity Mr beingable to secure sufficient play back output. In the average compositionin the above formula, it is possible to obtain both of thesecharacteristics and to secure a high SNR.

Protective Layer

The protective layer 15 includes, for example, a carbon material orsilicon dioxide (SiO2) and it is preferable to include a carbon materialfrom the viewpoint of the film strength of the protective layer 15.Examples of carbon materials include graphite, diamond-like carbon(DLC), diamonds, or the like.

Top Coat Layer

The top coat layer 16 includes, for example, a lubricant. It is possibleto use, for example, a silicone-based lubricant, a hydrocarbon-basedlubricant, a fluorinated hydrocarbon-based lubricant, or the like as alubricant.

2. Configuration of Sputtering Apparatus

As shown in FIG. 2, a sputtering apparatus according to one embodimentof the present technology is a continuous winding type sputteringapparatus and is provided with a film-forming chamber 21, a drum 22which is a metal can (a rotating body), cathodes 31 to 33, cathodeaccommodating chambers 51 to 53, a supply reel 23, a winding reel 24,and a plurality of guide rolls 25 and 26. The sputtering apparatus is,for example, a direct current (DC) magnetron sputtering type apparatus;however, the sputtering method is not limited to this type.

The film-forming chamber 21 is connected with a vacuum pump, which isnot shown in the diagram, via an exhaust port 27, and the atmosphereinside the film-forming chamber 21 is set to a predetermined degree ofvacuum by the vacuum pump. The drum 22, the supply reel 23, and thewinding reel 24 are arranged inside the film-forming chamber 21 with aconfiguration where rotation is possible. Inside the film-formingchamber 21, the plurality of guide rolls 25 for guiding transportationof the base material 11 between the supply reel 23 and the drum 22 areprovided and the plurality of guide rolls 26 for guiding transportationof the base material 11 between the drum 22 and the winding reel 24 areprovided. The base material 11 which is wound out from the supply reel23 is wound by the winding reel 24 via the guide roll 25, the drum 22,and the guide roll 26 during sputtering. The drum 22 has a columnarshape and the base material 11 with a strip shape is transported along aperipheral surface of the columnar surface shape of the drum 22. Acooling mechanism which is not shown in the diagram is provided in thedrum 22 and is cooled to, for example, approximately −20° C. duringsputtering.

The plurality of cathodes 31 to 33 are arranged opposing the peripheralsurface of the drum 22 and at equal intervals in the peripheraldirection of the drum 22 inside the film-forming chamber 21. It ispossible to attach targets 41 to 43 to the cathodes 31 to 33respectively. In a case of manufacturing a magnetic recording mediumwhich has the configuration described above, targets for film-formingthe lower coating layer 12, the intermediate layer 13, and the magneticrecording layer 14 are respectively set as the targets 41 to 43. Aplurality of types of films, for example, the three layers of the lowercoating layer 12, the intermediate layer 13, and the magnetic recordinglayer 14 are simultaneously film-formed by the cathodes 31 to 33 withone transportation of the base material 11.

The plurality of cathode accommodating chambers 51 to 53 foraccommodating each of the plurality of cathodes 31 to 33 are furtherarranged inside the film-forming chamber 21. The cathode accommodatingchambers 51 to 53 respectively have opening sections 61 to 63 on theside opposing the drum 22. Sputtering particles which are sputtered fromthe targets 41 to 43 and discharged into vapor reach the base material11 which is transported along the peripheral surface of the drum 22 viathe opening sections 61 to 63 and a thin film is formed.

The cathode accommodating chambers 51 to 53 are configured so as to beable to independently carry out vacuuming and exhausting inside theaccommodating chambers and to carry out heating and cooling control ofthe wall sections thereof. The cathode accommodating chambers 51 to 53may be configured such that it is possible to independently introduce aprocess gas to the accommodating chambers.

The atmosphere of the film-forming chamber 21 during sputtering is set,for example, to approximately 1×10⁻⁵ Pa to 5×10⁻⁵ Pa. It is possible tocontrol the film thickness and characteristics (for example, magneticcharacteristics) of the lower coating layer 12, the intermediate layer13, and the magnetic recording layer 14 by adjusting a tape line speedwhich winds the base material 11, the pressure (sputtering gas pressure)of Ar gas which is introduced during sputtering, supplied electricalpower, and the like. It is preferable that the tape line speed is withina range of approximately 1 m/min to 10 m/min. It is preferable that thesputtering gas pressure is within a range of approximately 0.1 Pa to 5Pa. It is preferable that the supplied electrical power amount is withina range of approximately 30 mW/mm2 to 150 mW/mm2.

In the sputtering apparatus which has the configuration described above,it is possible to continuously film-form the lower coating layer 12, theintermediate layer 13, and the magnetic recording layer 14 using a rollto roll method.

3. Method for Manufacturing Magnetic Recording Medium

Below, description will be given of one example of a method formanufacturing a magnetic recording medium according to one embodiment ofthe present technology with reference to FIG. 2 and FIG. 3A to FIG. 3C.Here, in each process shown below, since the cathode accommodatingchambers 51 to 53 are in substantially the same state, the state insidethe cathode accommodating chamber 51 is representatively shown in FIG.3A to FIG. 3C and the states of the other cathode accommodating chambers52 and 53 are omitted in the diagrams.

Process of Vacuuming and Exhausting

Firstly, the inside of the film-forming chamber 21 and the insides ofthe cathode accommodating chambers 51 to 53 are vacuumed and exhaustedto a predetermined degree of vacuum. In more detail, after the inside ofthe film-forming chamber 21 reaches a predetermined degree of vacuum dueto the vacuuming of the inside of the film-forming chamber 21, each ofthe chambers is set to a predetermined degree of vacuum by vacuuming theinsides of the cathode accommodating chambers 51 to 53. Alternatively,each of the chambers is set to a predetermined degree of vacuum bysimultaneously vacuuming and exhausting the inside of the film-formingchamber 21 and the insides of the cathode accommodating chambers 51 to53. The degree of vacuum of each of the cathode accommodating chambers51 to 53 is independently set, for example, according to thecharacteristics, composition, or the like of each layer which islaminated on the base material 11. In a state where the insides of thecathode accommodating chambers 51 to 53 are vacuumed, as shown in FIG.3A, gas 71 such as O₂ or H₂O remains on the inner wall surfaces of thecathode accommodating chambers 51 to 53.

Process of Heating Process

Next, it is preferable to carry out a heating process on the wallsections of the cathode accommodating chambers 51 to 53. This isbecause, due to this, it is possible to discharge the remaining gas 71such as O₂ or H₂O from the inner wall surfaces of the cathodeaccommodating chambers 51 to 53 as shown in FIG. 3B. From the viewpointof reducing the remaining gas 71, it is preferable to keep the innerwall surfaces of the cathode accommodating chambers 51 to 53 at 200° C.or higher for 30 minutes or longer by the heating process.

Film-forming Process of Lower Coating Layer, Intermediate Layer, andMagnetic Recording Layer

Next, the lower coating layer 12, the intermediate layer 13, and themagnetic recording layer 14 are film-formed on the base material 11. Indetail, the film-forming is carried out as follows. That is, the lowercoating layer 12, the intermediate layer 13, and the magnetic recordinglayer 14 are sequentially film-formed on a surface of the base material11 which moves along the peripheral surface of the drum 22 by carryingout sputtering on the targets 41 to 43 which are respectively set in thecathodes 31 to 33 while introducing a process gas such as Ar gas intothe film-forming chamber 21.

It is more preferable to continuously film-form all of the three layersof the lower coating layer 12, the intermediate layer 13, and themagnetic recording layer 14 on the surface of the moving base material11 in one process which winds out the base material 11 from the supplyreel 23 to be wound onto the winding reel 24 via the drum 22. Here, inthe one process which winds out the base material 11 from the supplyreel 23 to be wound onto the winding reel 24 via the drum 22, theremaining one layer (for example, the magnetic recording layer 14) maybe film-formed in a further process which film-forms two adjacent layers(for example, the lower coating layer 12 and the intermediate layer 13),winds out the base material 11 from the winding reel 24 again to bewound onto the supply reel 23. However, the former film-forming methodis preferable since there is a concern that deterioration in a surfacestate of a film will occur in the latter film-forming method.

In the film-forming process described above, it is preferable to carryout a cooling process on the wall sections of cathode accommodatingchambers 51 to 53. This is because, due to this, it is possible tosuppress discharge of the remaining gas 71 such as O₂ or H₂O whichremains on the inner wall surfaces of the cathode accommodating chambers51 to 53 as shown in FIG. 3C. From the viewpoint of suppressingdischarge of the remaining gas 71, it is preferable to keep thetemperature of the inner wall surfaces of the cathode accommodatingchambers 51 at 53 at 90° C. or less during the film-forming.

Film-Forming Process of Protective Layer

Next, for example, the base material 11 which is wound onto the windingreel 24 is transported from a sputtering apparatus to anotherfilm-forming apparatus and the protective layer 15 is film-formed on thesurface of the magnetic recording layer 14. It is possible to use, forexample, a chemical vapor deposition (CVD) method or a physical vapordeposition (PVD) method as a method for film-forming the protectivelayer 15.

Film-Forming Process of Top Coat Layer

Next, for example, the base material 11 is transported to a coatingapparatus, a lubricant or the like is coated on a surface of theprotective layer 15, and the top coat layer 16 is film-formed. It ispossible to use various types of coating methods, for example, such asgravure coating and dip coating as the lubricant coating method.

Due to the above, the magnetic recording medium shown in FIG. 1 isobtained.

4. Effects

In the magnetic recording medium according to the present embodiment,since variation in magnetic characteristics is suppressed within ±10%over a division of 300 m in a longitudinal direction of a magneticrecording medium with a strip shape, it is possible to stabilizemagnetic characteristics in the longitudinal direction of the magneticrecording medium. That is, it is possible to provide a magneticrecording medium which has excellent reliability. In addition, it ispossible to provide a magnetic recording medium with excellent inmagnetic characteristics where recording is possible by a head forin-plane magnetic recording and the intermediate layer 13 and themagnetic recording layer 14 have favorable crystal orientation growth.

In the sputtering apparatus according to the present embodiment, sinceeach of the cathodes 31 to 33 is covered by the cathode accommodatingchambers 51 to 53 in an individual accommodating chamber, it is possibleto secure the stability of the magnetic characteristics in thelongitudinal direction of the magnetic recording medium. In a case wherethe cathode accommodating chambers 51 to 53 are not provided, withoutbeing able to control the optimum gas pressure of each laminated film,defects are generated such as not being able to secure the desired filmcharacteristics, not being able to hold the characteristic stability bybeing influenced across the board by the degassing, and the like.

In the sputtering apparatus according to the present embodiment, in acase of keeping the inner wall surfaces of the cathode accommodatingchambers 51 to 53 at a certain temperature or less during the continuoussputtering film-forming, it is possible to suppress discharging of theremaining gas 71 from the inner wall surfaces and improve the stabilityof magnetic characteristics in the longitudinal direction of a magneticrecording medium.

5. Modified Examples

In the embodiment described above, description was given of exampleswhere the present technology was applied with respect to a magneticrecording medium which has a configuration where the lower coating layer12, the intermediate layer 13, and the magnetic recording layer 14 aresequentially laminated on the base material 11, a method formanufacturing the same, and a sputtering apparatus; however, the presenttechnology is not limited thereto.

Modified Example 1

As shown in FIG. 4, a magnetic recording medium may have a configurationwhere the intermediate layer 13 between the lower coating layer 12 andthe magnetic recording layer 14 (refer to FIG. 1) is omitted and thelower coating layer 12 and the magnetic recording layer 14 are adjacent.A sputtering apparatus for manufacturing the magnetic recording mediumhas a configuration where the cathode 32 and the cathode accommodatingchamber 52 in the sputtering apparatus shown in FIG. 2 are omitted. Themethod for manufacturing the magnetic recording medium is the same asthe method for manufacturing the magnetic recording medium according tothe first embodiment apart from sequentially laminating the lowercoating layer 12 and the magnetic recording layer 14 on the basematerial 11 using the sputtering apparatus which has the configurationdescribed above.

Modified Example 2

As shown in FIG. 5, a magnetic recording medium may be further providedwith a lower coating layer 17 and a soft magnetic underlayer (referredto below as “SUL”) 18 between the base material 11 and the lower coatinglayer 12. The lower coating layer 17 is provided on the base material 11side and the SUL 18 is provided on the lower coating layer 12 side. Inaddition, a CAP layer (a stack layer) 19 may be further provided betweenthe magnetic recording layer 14 and the protective layer 15. The lowercoating layer 17, the SUL 18, and the CAP layer 19 may all be provided;however, one or more types out of these layers may be provided.

Lower Coating Layer

It is possible to use the same lower coating layer as the lower coatinglayer 12 in the first embodiment as the lower coating layer 17.

SUL

The film thickness of the SUL 18 is preferably 40 nm or more, morepreferably 40 nm or more to 140 nm or less. When the film thickness isless than 40 nm, there is a tendency for the recording and play backcharacteristics to decrease. On the other hand, when the film thicknessexceeds 140 nm, the decrease in the crystal orientation of theintermediate layer 13 due to coarsening of the crystal particles of theSUL 18 is remarkable, the film-forming time of the SUL 18 is longer, andthere is a concern that a decrease in productivity will occur. The SUL18 includes a soft magnetic material in an amorphous state. It ispossible to use, for example, a Co-based material, a Fe-based material,or the like as the soft magnetic material. Examples of the Co-basedmaterial include CoZrNb, CoZrTa, CoZrTaNb, and the like. Examples of theFe-based material include FeCoB, FeCoZr, FeCoTa, and the like.

Since the SUL 18 has an amorphous state, the SUL 18 does not play a roleof promoting epitaxial growth in a layer which is formed on the SUL 18;however, there is a demand to not disturb crystal orientation of theintermediate layer 13 which is formed on the SUL 18. For that, it ispreferable to have a minute structure where the soft magnetic materialdoes not form a column; however, in a case where the influence ofdegassing such as water from the base material 11 is large, there is aconcern that the soft magnetic material will be coarsened and disturbthe crystal orientation of the intermediate layer 13 which is formed onthe SUL 18. In order to suppress these influences, it is preferable thatthe lower coating layer 17 is provided on the surface of the basematerial 11. In particular, in a case of using a polymer material film,in which a large amount of water or gasses such as oxygen are absorbed,as the base material 11, it is preferable that the lower coating layer17 is provided in order to suppress these influences.

The SUL 18 may be an antiparallel coupled SUL (referred to below as“APC-SUL”). The APC-SUL has a structure where two soft magnetic layersare laminated via a thin intermediate layer and magnetization isactively coupled in antiparallel using exchange coupling via theintermediate layer. It is preferable that the film thickness of the softmagnetic layer be substantially the same. The total film thickness ofthe soft magnetic layer is preferably 40 nm or more, more preferably 40nm or more to 70 nm or less. When the film thickness is less than 40 nm,there is a tendency for the recording and play back characteristics todecrease. On the other hand, when the film thickness exceeds 70 nm, thefilm-forming time of the APC-SUL is longer and there is a concern that adecrease in productivity will occur. It is preferable that the materialof a soft magnetic layer is the same material and it is possible to usethe same material as the SUL 18 described above as the material. Thefilm thickness is, for example, 0.8 nm or more to 1.4 nm or less,preferably 0.9 nm or more to 1.3 nm or less, and more preferablyapproximately 1.1 nm. It is possible to obtain more favorable recordingand play back characteristics by selecting the film thickness of theintermediate layer within a range of 0.9 nm or more to 1.3 nm or less.Examples of a material of an intermediate layer include V, Cr, Mo, Cu,Ru, Rh, Re, and the like, and Ru is particularly preferable.

CAP Layer

A laminated structure formed of the magnetic recording layer 14 whichhas a granular structure and the CAP layer 19 is generally referred toas coupled granular continuous (CGC). It is preferable that the filmthickness of the CAP layer 19 is 4 nm or more to 12 nm or less. It ispossible to obtain more favorable recording and play backcharacteristics by selecting a film thickness of the CAP layer 19 withina range of 4 nm or more to 12 nm or less. The CAP layer 19 includes, forexample, a CoCrPt-based material. Examples of the CoCrPt-based materialinclude CoCrPt, CoCrPtB, a material where a metal oxide is further addedto these materials (CoCrPt-metal oxide or CoCrPtB-metal oxide), and thelike. It is possible to use at least one type which is selected from agroup formed of, for example, Si, Ti, Mg, Ta, Cr, and the like as ametal oxide to be added. Specific examples thereof include SiO₂, TiO₂,MgO, Ta₂O₅, Cr₂O₃, a mixture of two or more types thereof, and the like.

A sputtering apparatus for manufacturing the magnetic recording mediummay be provided with a number, which is equivalent to the number oflayers of laminated films which are film-formed on the base material 11,of the cathodes 31 to 33 and the cathode accommodating chambers 51 to 52in the sputtering apparatus shown in FIG. 2. In more detail, forexample, 6 cathodes and cathode accommodating chambers may be provided,which is equivalent to the number of the 6 layers of the lower coatinglayer 17, the SUL 18, the lower coating layer 12, the intermediate layer13, the magnetic recording layer 14, and the CAP layer 19. The methodfor manufacturing the magnetic recording medium is the same as themethod for manufacturing the magnetic recording medium according to thefirst embodiment apart from sequentially laminating the lower coatinglayer 17, the SUL 18, the lower coating layer 12, the intermediate layer13, the magnetic recording layer 14, and the CAP layer 19 on the basematerial 11 using a sputtering apparatus which has the configurationdescribed above.

EXAMPLES

Below, detailed description will be given of the present technologyusing examples; however, the present technology is not only limited tothese examples.

Description will be given of examples of the present technology in thefollowing order.

i. Relationships between an inner wall surface temperature and an H₂Opartial pressure and between an H₂O partial pressure and magneticcharacteristics

ii. A relationship between sputtering discharge time, an inner wallsurface temperature, and magnetic characteristics

iii. A relationship between sputtering film-forming length, an H₂Opartial pressure, and magnetic characteristics

i. A Relationship Between an Inner Wall Surface Temperature and an H₂OPartial Pressure and Between an H₂O Partial Pressure and MagneticCharacteristics Reference Example 1

Using a sputtering apparatus which has the configuration shown in FIG.2, a magnetic tape was manufactured as follows. Here, in the presentembodiment, the same reference numerals are given to the portions whichcorrespond to the embodiment described above.

Firstly, the targets 41 to 43 below were respectively attached to thecathodes 31 to 33.

Target 41: Ti₃₀Cr₇₀ target

Target 42: Ru target

Target 43: (Co₇₅Cr₁₀Pt₁₅)₉₀—(SiO₂)₁₀ target

Next, the inside of the film-forming chamber 21 and the insides of thecathode accommodating chambers 51 to 53 were vacuumed. Here, it waspossible to obtain a degree of vacuum appropriate for the film qualityof a thin film which is film-formed by each of the targets 41 to 43 byindependently carrying out vacuuming and exhausting control of thecathode accommodating chambers 51 to 53. Next, film-forming wasperformed as follows without performing a heating process on the wallsections of the cathode accommodating chambers 51 to 53. That is, thelower coating layer 12, the intermediate layer 13, and the magneticrecording layer 14 were sequentially film-formed on the surface of themoving polymer film 11 with a strip shape by carrying out sputtering onthe targets 41 to 43 which were respectively attached to the cathodes 31to 33 while introducing Ar gas into the film-forming chamber 21. Inaddition, the temperature of the inner wall surface of the cathodeaccommodating chambers 51 to 53 and an H₂O partial pressure inside thecathode accommodating chambers 51 to 53 during the film-forming of eachlayer were measured. Here, temperature control of wall sections of thecathode accommodating chambers 51 to 53 was not performed during thefilm-forming. Due to the above, a magnetic tape with a strip shape wasobtained.

Next, coercive force (Hc) of the magnetic recording layer 14 of theobtained magnetic tape was obtained using a vibrating samplemagnetometer (VSM). Next, variation in the obtained coercive force wasdetermined by the following formula.

(Variation in coercive force)=100−[((coercive force of a magnetic tapemanufactured at a predetermined inner wall surfacetemperature)/(coercive force of a magnetic tape manufactured at an innerwall surface temperature of 20° C.))×100][%]

Measurement Result

Table 1 shows measurement results of the temperature of an inner wallsurface of the cathode accommodating chamber 51 and the H₂O partialpressure inside the cathode accommodating chamber 51 when manufacturingthe magnetic tape in the reference example 1. In addition, measurementresults of the coercive force of a magnetic tape which is manufacturedat each inner wall surface temperature and variations thereof are alsoshown. FIG. 6A shows a relationship between the inner wall surfacetemperature of the cathode accommodating chamber 51 and the H₂O partialpressure inside the cathode accommodating chamber 51. FIG. 6B shows arelationship between the H₂O partial pressure inside the cathodeaccommodating chamber 51 and the coercive force of the magneticrecording layer 14. Here, since the inner wall surface temperature andthe H₂O partial pressure of each of the cathode accommodating chambers51 to 53 are substantially the same, only the inner wall surfacetemperature and the H₂O partial pressure of the cathode accommodatingchamber 51 are representatively shown in Table 1, FIG. 6A, and FIG. 6B.

TABLE 1 Reference Example 1 Temperature of inner H₂O Partial wallsection Pressure ⊥ Hc ⊥ Hc Variation [° C.] [Pa] [Oe] [%] 20 4.00 × 10⁻⁵3050 — 40 5.00 × 10⁻⁵ 3000 1.64 60 6.00 × 10⁻⁵ 2960 2.95 80 7.50 × 10⁻⁵2900 4.92 90 1.00 × 10⁻⁴ 2700 11.48 100 3.00 × 10⁻⁴ 1900 37.70 120 4.50× 10⁻⁴ 1500 50.82

The following is understood from the measurement results describedabove.

H₂O Partial Pressure

There is a tendency for the H₂O partial pressure inside the cathodeaccommodating chambers 51 to 53 to increase in accordance with anincrease in the temperature of the inner wall surface of the cathodeaccommodating chambers 51 to 53. In particular, when the temperature ofthe inner wall surfaces of the cathode accommodating chambers 51 to 53is 90° C. or higher, the degree of increase in the H₂O partial pressureinside the cathode accommodating chambers 51 to 53 is remarkable.

Magnetic Characteristics

There is a tendency for the coercive force to decrease in accordancewith an increase in the H₂O partial pressure inside the cathodeaccommodating chambers 51 to 53. In particular, when the H₂O partialpressure inside the cathode accommodating chambers 51 to 53 is 1.00×10⁻⁴or more, the degree of decrease in the coercive force is remarkable.Here, only the measurement results of coercive force are shown as themagnetic characteristics; however, the squareness ratio and theorientation strength Δθ₅₀ of the magnetic recording layer 14 also showthe same tendency with respect to an increase in the H₂O partialpressure inside the cathode accommodating chambers 51 to 53.

ii. A Relationship Between Sputtering Discharge Time, an Inner WallSurface Temperature, and Magnetic Characteristics Example 1

Using a sputtering apparatus which has the configuration shown in FIG.2, the magnetic tape was manufactured as follows. Firstly, the targets41 to 43 which are the same as the reference example 1 were respectivelyattached to the cathodes 31 to 33. Next, the inside of the film-formingchamber 21 and the insides of the cathode accommodating chambers 51 to53 were vacuumed. Here, it was possible to obtain a degree of vacuumappropriate for the film quality of a thin film which is film-formed byeach of the targets 41 to 43 by independently carrying out vacuuming andexhausting control of the cathode accommodating chambers 51 to 53. Next,after heating a wall section of each of the cathode accommodatingchambers 51 to 53 and keeping the temperature of the inner wall surfacesof the cathode accommodating chambers 51 to 53 at 200° C. or higher for30 minutes or longer, film-forming was performed as follows. That is,the lower coating layer 12, the intermediate layer 13, and the magneticrecording layer 14 were sequentially film-formed on the surface of themoving polymer film 11 with a strip shape by carrying out sputtering onthe targets 41 to 43 which were respectively attached to the cathodes 31to 33 while introducing Ar gas into the film-forming chamber 21. Here,temperature control was performed which cooled the wall sections of thecathode accommodating chambers 51 to 53 during film-forming to keep atemperature of 90° C. or lower. In addition, the temperature of theinner wall surfaces of the cathode accommodating chambers 51 to 53during film-forming was measured. Due to the above, a magnetic tape witha strip shape was obtained.

Next, the coercive force (Hc) of the magnetic recording layer 14 of theobtained magnetic tape is determined using a vibrating samplemagnetometer. Next, variation in the obtained coercive force wasdetermined by the following formula.

(Variation in coercive force)=100−[((coercive force of a magnetic tapemanufactured after a predetermined discharge time passes)/(coerciveforce of a magnetic tape manufactured after discharge time of 5 minutespasses))×100][%]

Reference Example 2

A magnetic tape was manufactured in the same manner as the referenceexample 1 and the temperature of the inner wall surfaces of the cathodeaccommodating chambers 51 to 53 during film-forming was measured. Next,the coercive force (Hc) of the magnetic recording layer 14 of theobtained magnetic tape and variations thereof were obtained in the samemanner as example 1.

Measurement Results

Table 2 shows the inner wall surface temperature of the cathodeaccommodating chamber 51 when manufacturing the magnetic tape in example1 and the reference example 2, the coercive force of the magnetic tapewhich is manufactured at each inner wall surface temperature, andvariations thereof. FIG. 7A shows a relationship between the sputteringdischarge time and the inner wall surface temperature of the cathodeaccommodating chambers 51 to 53. FIG. 7B shows a relationship betweenthe sputtering discharge time and the coercive force of the magneticrecording layer 14. Here, since changes in the temperature of the innerwall surfaces of each of the cathode accommodating chambers 51 to 53 aresubstantially the same, only the changes in the temperature of thecathode accommodating chamber 51 are representatively shown in Table 2and FIG. 7A.

TABLE 2 Reference Example 2 Example 1 Temperature Dis- Temperature ofcharge of inner ⊥ Hc inner wall ⊥ Hc Time wall section ⊥ Hc Variationsection ⊥ Hc Variation [min] [° C.] [Oe] [%] [° C.] [Oe] [%] 5 20 2990 —20 3050 — 10 40 3010 −0.67 40 3000 1.64 15 55 2980 0.33 60 2960 2.95 2060 2950 1.34 80 2900 4.92 25 65 2930 2.01 90 2700 11.48 35 70 2920 2.34110 1900 37.70 40 72 2940 1.67 115 1500 50.82

The following is understood from the measurement results describedabove.

Temperature of Inner Wall Surface

In reference example 2, there is a tendency for the temperature of theinner wall surface of the cathode accommodating chambers 51 to 53 toincrease in accordance with the sputtering discharge time. On the otherhand, in example 1, there is a tendency for the temperature of the innerwall surface of the cathode accommodating chambers 51 to 53 to increasein accordance with the sputtering discharge time when the sputteringdischarge time is less than 15 minutes; however, when the sputteringdischarge time is 15 minutes or longer, the degree of increase in thetemperature of the inner wall surface of the cathode accommodatingchambers 51 to 53 becomes small and substantially constant.

Magnetic Characteristics

In reference example 2, the coercive force is substantially constantregardless of the sputtering discharge time when the sputteringdischarge time is in a range of less than 20 minutes; however, when thesputtering discharge time is 20 minutes or longer, there is a tendencyfor the coercive force to greatly decrease. On the other hand, inexample 1, when the sputtering discharge time is 20 minutes or longer,there is a tendency for the coercive force to be held to besubstantially constant regardless of the sputtering discharge time.Here, only the measurement results of coercive force are shown as themagnetic characteristics; however, the squareness ratio and theorientation strength Δθ₅₀ of the magnetic recording layer 14 also showthe same tendency with respect to an increase in the sputteringdischarge time.

Variation in Magnetic Characteristics

In reference example 2, variation in the coercive force after 40 minutesof film-forming greatly exceeds 10%. On the other hand, in example 1,variation in the coercive force after 40 minutes of film-forming issuppressed to less than 10%. Here, only variation in the coercive forceis shown as the magnetic characteristics; however, the squareness ratioand the orientation strength Δθ₅₀ of the magnetic recording layer 14also show the same tendency with respect to the increase in the H₂Opartial pressure inside the cathode accommodating chambers 51 to 53.

iii. A Relationship Between Sputtering Film-Forming Length, an H₂OPartial Pressure, and Magnetic Characteristics Example 2

A magnetic tape was manufactured in the same manner as example 1 and anH₂O partial pressure inside the cathode accommodating chambers 51 to 53was measured. Next, the coercive force (Hc) and the squareness ratio ofthe magnetic recording layer 14 of the obtained magnetic tape weredetermined using a vibrating sample magnetometer. Next, variations inthe obtained coercive force and squareness ratio were obtained by thefollowing formula.

(Variation in coercive force)=100−[((coercive force after predeterminedsputtering film-forming length film-forming)/(coercive force ofsputtering film-forming length of substantially 0 m))×100][%]

(Variation in squareness ratio)=100−[((squareness ratio afterpredetermined sputtering film-forming length film-forming)/(squarenessratio of sputtering film-forming length of substantially 0 m))×100][%]

Here, the sputtering film-forming length has the meaning of the lengthof a laminated film which is continuously film-formed in a longitudinaldirection of a polymer film with a strip shape (a laminated film of thelower coating layer 12, the intermediate layer 13, and the magneticrecording layer 14).

Next, the orientation strength Δθ₅₀ was determined by measuringdiffraction peaks of magnetic atoms included in the magnetic recordinglayer 14 in X-ray diffraction peaks of the magnetic tape using a lockingcurve method. Next, a variation in the obtained orientation strengthΔθ₅₀ was determined by the following formula.

(Variation in Δθ₅₀)=100−[((orientation strength Δθ₅₀ after predeterminedsputtering film-forming length film-forming)/(orientation strength Δθ₅₀of sputtering film-forming length of substantially 0 m))×100][%]

Reference Example 3

A magnetic tape was manufactured in the same manner as the referenceexample 1 and the H₂O partial pressure inside the cathode accommodatingchambers 51 to 53 was measured. Next, the coercive force (Hc), thesquareness ratio, the orientation strength Δθ₅₀, and variations thereofof the magnetic recording layer 14 of the obtained magnetic tape weredetermined in the same manner as example 2.

Measurement Results

Table 3 and Table 4 each show the H₂O partial pressure inside thecathode accommodating chamber 51 when manufacturing the magnetic tape inexample 2 and reference example 3, and the coercive force, thesquareness ratio, orientation strength Δθ₅₀, and variations thereof inmagnetic tapes manufactured at each pressure. FIG. 8A shows arelationship between a sputtering film-forming length and the H₂Opartial pressure inside the cathode accommodating chamber 51. FIG. 8Bshows a relationship between the sputtering film-forming length and thecoercive force. FIG. 9A shows a relationship between the sputteringfilm-forming length and the squareness ratio. FIG. 9B shows arelationship between the sputtering film-forming length and theorientation strength Δθ₅₀ of the magnetic recording layer 14. Here,since changes in the partial pressure of the inner wall surfaces of eachof the cathode accommodating chambers 51 to 53 are substantially thesame, only the changes in the partial pressure of the cathodeaccommodating chamber 51 are representatively shown in Table 3 and FIG.8A.

TABLE 3 Example 2 Sputtering ⊥ Hc ⊥ Rs Δθ₅₀ H₂O film-forming Variation ⊥Rs Variation Δθ₅₀ Variation Partial length [m] ⊥ Hc [Oe] [%] [%] [%] [°][%] Pressure [Pa] 0 2990 — 83.0 — 7.3 — 4.00 × 10⁻⁵ 200 3010 −0.67 84.0−1.20 7.2 1.37 5.00 × 10⁻⁵ 400 2980 0.33 83.1 −0.12 7.4 −1.37 5.50 ×10⁻⁵ 600 2970 0.67 83.5 −0.60 7.3 0.00 5.40 × 10⁻⁵ 800 3020 −1.00 84.5−1.81 7.4 −1.37 5.30 × 10⁻⁵ 1000 2975 0.50 83.4 −0.48 7.2 1.37 5.10 ×10⁻⁵

TABLE 4 Sputtering Example 3 film-forming ⊥ Hc ⊥ Rs Δθ₅₀ H₂O Partiallength ⊥ Hc Variation ⊥ Rs Variation Variation Pressure [m] [Oe] [%] [%][%] Δθ₅₀ [°] [%] [Pa] 0 3020 — 84.5 — 7.2 — 4.00 × 10⁻⁵ 200 2015 33.2872.4 14.32 8.3 −15.28 2.00 × 10⁻⁴ 400 1880 37.75 70.3 16.80 8.1 −12.504.00 × 10⁻⁴ 600 2010 33.44 75.7 10.41 7.5 −4.17 2.10 × 10⁻⁴ 800 245018.87 80.8 4.38 7.4 −2.78 1.20 × 10⁻⁴ 1000 2680 11.26 82.0 2.96 7.2 0.006.00 × 10⁻⁵

The following is understood from the measurement results describedabove.

H₂O Partial Pressure

In reference example 3, while the H₂O partial pressure increases inaccordance with the sputtering film-forming length becoming longer whenthe sputtering film-forming length is less than 400 m, there is atendency for the H₂O partial pressure to decrease in accordance with thesputtering film-forming length becoming longer when the sputteringfilm-forming length is 400 m or longer. On the other hand, in example 2,there is a tendency for the H₂O partial pressure to be staysubstantially constant without depending on the sputtering length.

Magnetic Characteristics

In reference example 3, while the coercive force and the squarenessratio decrease in accordance with the sputtering film-forming lengthbecoming longer when the sputtering film-forming length is less than 400m, there is a tendency for the coercive force and the squareness ratioto increase when the sputtering film-forming length is 400 m or longer.On the other hand, in example 2, there is a tendency for the coerciveforce and the squareness ratio to be kept substantially constant withoutdepending on the sputtering length.

In reference example 3, while the orientation strength Δθ₅₀ of themagnetic recording layer 14 is widened in accordance with the sputteringfilm-forming length becoming longer when the sputtering film-forminglength is less than 200 m, there is a tendency for the orientationstrength Δθ₅₀ of the magnetic recording layer 14 to be narrowed when thesputtering film-forming length is 200 m or longer. On the other hand, inexample 2, there is a tendency for the orientation strength Δθ₅₀ of themagnetic recording layer 14 to be kept substantially constant withoutdepending on the sputtering length.

Variation in Magnetic Characteristics

In reference example 3, variations in the coercive force, squarenessratio, and orientation strength Δθ₅₀ of the magnetic recording layer 14exceed ±10% in a division of 200 m or less in the longitudinal directionof the magnetic tape. On the other hand, in example 2, variations in thecoercive force, squareness ratio, and orientation strength Δθ₅₀ of themagnetic recording layer 14 are within ±10% over a division of 1000 m inthe longitudinal direction of the magnetic tape.

Above, detailed description was given of embodiments of the presenttechnology and modified examples and examples thereof; however, thepresent technology is not limited to the embodiments and modifiedexamples and examples thereof described above and various types ofmodifications are possible based on the technical idea of the presenttechnique.

For example, the configurations, the methods, the processes, the shapes,the materials, the numeric values, and the like which are given in theembodiments and the modified examples and examples thereof are merelyexamples and configurations, methods, processes, shapes, materials,numeric values, and the like which are different therefrom may be usedas necessary.

In addition, the configurations, the methods, the processes, the shapes,the materials, the numeric values, and the like of the embodiments andthe modified examples and examples thereof described above are able tobe combined with each other within a scope which does not depart fromthe gist of the present technique.

In addition, the present technology is also able to adopt the followingconfigurations.

(1) A magnetic recording medium including a base material which hasflexibility, and a laminated film, in which a variation in magneticcharacteristics is within □10% over a division of 300 m in alongitudinal direction of the base material.

(2) The magnetic recording medium according to (1), in which thelaminated film includes a lower coating layer and a perpendicularrecording layer.

(3) The magnetic recording medium according to (2), in which the lowercoating layer includes Ti and Cr, and the perpendicular recording layerhas a granular structure where particles which include Co, Pt, and Crare separated by an oxide.

(4) The magnetic recording medium according to (2) or (3), in which thelower coating layer has an amorphous state.

(5) The magnetic recording medium according to any one of (2) to (4), inwhich the laminated film further includes an intermediate layer.

(6) The magnetic recording medium according to (5), in which theintermediate layer includes Ru or NiW.

(7) The magnetic recording medium according to any one of (2) to (6), inwhich the laminated film further includes at least one type of layer outof a soft magnetic layer and a CAP layer.

(8) The magnetic recording medium according to any one of (1) to (7), inwhich a variation in magnetic characteristics is within ±5% over adivision of 300 m or more in the longitudinal direction of the basematerial.

(9) The magnetic recording medium according to any one of (1) to (8), inwhich the magnetic characteristics are a holding power Hc, a squarenessratio Rs, and an orientation strength Δθ₅₀.

(10) The magnetic recording medium according to any one of (1) to (9),in which the laminated film is film-formed by a physical depositionmethod.

(11) The magnetic recording medium according to (10), in which thephysical deposition method is a sputtering method.

(12) A film-forming apparatus including a rotating body which moves abase material with a strip shape which has flexibility, a plurality ofcathodes which are provided to oppose a rotating surface of the rotatingbody, and a plurality of accommodating sections which accommodate eachof the plurality of cathodes.

(13) The film-forming apparatus according to (12), in which theplurality of accommodating sections are configured so as to be able toexhaust a vacuum and to carry out heating and cooling.

(14) A method for manufacturing a magnetic recording medium includingsequentially film-forming a plurality of thin films on a base materialusing a plurality of cathodes which are provided on a moving path of thebase material while moving the base material with a strip shape whichhas flexibility, in which each of the plurality of cathodes isaccommodated in the plurality of accommodating sections.

(15) The method for manufacturing a magnetic recording medium accordingto (14), further including heating the plurality of accommodatingsections before film-forming the plurality of thin films.

(16) The method for manufacturing a magnetic recording medium accordingto (15), in which a temperature of inner walls of the plurality ofaccommodating sections is held at 200° C. or higher for 30 minutes orlonger by the heating.

(17) The method for manufacturing a magnetic recording medium accordingto any one of (14) to (16), further including cooling the plurality ofaccommodating sections while film-forming the plurality of thin films.

(18) The method for manufacturing a magnetic recording medium accordingto (17), in which the temperature of inner walls of the plurality ofaccommodating sections is held at 90° C. or lower by the cooling. Itshould be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The invention is claimed as follows:
 1. A magnetic recording mediumcomprising: a base material which has flexibility; and a laminated film,wherein a variation in magnetic characteristics is within ±10% over adivision of 300 m in a longitudinal direction of the base material. 2.The magnetic recording medium according to claim 1, wherein thelaminated film includes a lower coating layer and a perpendicularrecording layer.
 3. The magnetic recording medium according to claim 2,wherein the lower coating layer includes Ti and Cr, and theperpendicular recording layer has a granular structure where particleswhich include Co, Pt, and Cr are separated by an oxide.
 4. The magneticrecording medium according to claim 2, wherein the lower coating layerhas an amorphous state.
 5. The magnetic recording medium according toclaim 2, wherein the laminated film further includes an intermediatelayer.
 6. The magnetic recording medium according to claim 5, whereinthe intermediate layer includes Ru or NiW.
 7. The magnetic recordingmedium according to claim 2, wherein the laminated film further includesat least one type of layer out of a soft magnetic layer and a CAP layer.8. The magnetic recording medium according to claim 1, wherein avariation in magnetic characteristics is within ±5% over a division of300 m or more in the longitudinal direction of the base material.
 9. Themagnetic recording medium according to claim 1, wherein the magneticcharacteristics are a holding power Hc, a squareness ratio Rs, and anorientation strength Δθ₅₀.
 10. The magnetic recording medium accordingto claim 1, wherein the laminated film is film-formed by a physicaldeposition method.
 11. The magnetic recording medium according to claim10, wherein the physical deposition method is a sputtering method.
 12. Afilm-forming apparatus comprising: a rotating body which moves a basematerial with a strip shape which has flexibility; a plurality ofcathodes which are provided to oppose a rotating surface of the rotatingbody; and a plurality of accommodating sections which accommodate eachof the plurality of cathodes.
 13. The film-forming apparatus accordingto claim 12, wherein the plurality of accommodating sections areconfigured so as to be able to exhaust a vacuum and to carry out heatingand cooling.
 14. A method for manufacturing a magnetic recording mediumcomprising: sequentially film-forming a plurality of thin films on abase material using a plurality of cathodes which are provided on amoving path of the base material while moving the base material with astrip shape which has flexibility, wherein each of the plurality ofcathodes is accommodated in a plurality of accommodating sections. 15.The method for manufacturing a magnetic recording medium according toclaim 14, further comprising: heating the plurality of accommodatingsections before film-forming the plurality of thin films.
 16. The methodfor manufacturing a magnetic recording medium according to claim 15,wherein a temperature of inner walls of the plurality of accommodatingsections is held at 200° C. or higher for 30 minutes or longer by theheating.
 17. The method for manufacturing a magnetic recording mediumaccording to claim 14 further comprising: cooling the plurality ofaccommodating sections while film-forming the plurality of thin films.18. The method for manufacturing a magnetic recording medium accordingto claim 17, wherein the temperature of inner walls of the plurality ofaccommodating sections is held at 90° C. or lower by the cooling.